Compute the normal of a 2D spline using animation nodes
The normal to a point on a spline is equal to the tangent at this point rotated by 90 degrees around the z axis. Let the tangent be $\vec{t} = (x, y)$, then the normal is equal to $R\vec{t}$, where $R$ is a 2D rotation matrix with an angle of $\frac{\pi}{2}$. So the normal is equal to:

$$
\begin{bmatrix}
\cos \frac{\pi}{2} &amp; -\sin \frac{\pi}{2} \\
\sin \frac{\pi}{2} &amp; \cos \frac{\pi}{2}
\end{bmatrix}
\begin{bmatrix}
x \\
y
\end{bmatrix} = 
\begin{bmatrix}
0 &amp; -1 \\
1 &amp; 0
\end{bmatrix}
\begin{bmatrix}
x \\
y
\end{bmatrix} = 
\begin{bmatrix}
-y \\
x
\end{bmatrix}
$$

So, given the evaluated tangents, you can compute the normals as follows:



To deform an object as described in the answer you linked, you will need a third vector, the one we computed using the cross product. In this case, it will always be the vector $(0, 0, 1)$.